Electron-positron pair production in the external electromagnetic field of colliding relativistic heavy ions

The results concerning the c(+)c(-) production in peripheral highly relativistic heavy-ion collisions presented in a recent paper by Baltz et al. are rederived in a very straightforward manner. It is shown that the solution of the Dirac equation directly leads to the multiplicity, i.e. to the total number of electron-position pairs produced by the electromagnetic field of the ions, whereas the calculation of the single pair production probability is much more involved. A critical observation concerns the unsolved problem of seemingly absent Coulomb corrections (Bethe-Maximon corrections) in pair production cross sections. It is shown that neither the inclusion of the vacuum-vacuum amplitude nor the correct interpretation of the solution of the Dirac equation concerning the pair multiplicity is able the explain (from a fundamental point of view) the absence of Coulomb corrections. Therefore the contradiction has to be accounted to the treatment of the high energy limit.